Pressure sensitive record material



June 17, 196g J. M. aTLLE-'r ET AL 3,450,553v

PRESSURE SENSITIVE RECORD MATERIAL FIGB Filed Jan. 5, .1966

4 I2 Il ol .oToIoo o ol INVENT ORS JAMES M. BILLET MICHAEL T. ORINIKJAMES 0. THOMPSON United States Patent O 3,450,553 PRESSURE SENSITIVERECORD MATERIAL James M. Billet, Endicott, Michael T. Orinik,Binghamton,

and James O. Thompson, Endwell, N.Y., assignors to InternationalBusiness Machines Corporation, Armonk,

N.Y., a corporation of New York Filed Jan. 3, 1966, Ser. No. 518,275Int. Cl. D21h I/22, 3/80; B32b 29/06 U.S. Cl. 117-361 21 Claims ABSTRACTF THE DISCLOSURE A pressure sensitive record material which comprises asheet of paper containing at least about five percent lignin and asubstantially colorless reactant which reacts with lignin under writingpressure to form fvisible reaction products. The reactant includesphenolic materials such as phloroglucinol, aromatic bases such asaniline hydrochloride, heterocyclic compounds such as 3 -aminopyridineand inorganic compounds such as cobalt, thiocyanate.

The present invention relates to new pressure sensitive recordmaterials. The principles of the invention are adaptable both to singleelement copy systems .and to multiple element arrangements similar toconventional manifolding packs.

The purpose of the invention is to provide reliable pressure sensitiverecord materials which produce clear and durable copies without the needfor using carbon papers or similar transfer materials. A further objectof the invention is to provide pressure sensitive record materials whichhave good shelf life and which are resistant to smudging or smearing asa result of normal handling.

In general, the pressure sensitive record materials of the presentinvention comprise a sheet of paper containing lignin. A color precursoris associated with the sheet of paper, so that upon the application ofpressure, the lignin and the color precursor react to form Visiblemarkings. The color precursor may be incorporated in the body of thesheet of paper in a passive form and be rendered active by applicationof pressure. Alternatively, the color precursor may be carried on thesurface of the paper sheet or on the surface of another associatedelement, so that upon application of pressure the lignin and colorprecursor are brought together to form the desired reaction products.

The present invention will be more fully appreciated in view of thefollowing detailed description of certain preferred embodimentsconsidered in the light of the o accompanying drawing.

In the drawing:

FIGURES 1 and 2 are schematic, cross-sectional, edge views of sheets ofrecord material in accordance with the invention,

FIGURE 3 is a schematic, cross-sectional, edge View of a two-sheetmanifolding pack utilizing record material of the present invention, and

FIGURE 4 is a somewhat schematic, cross-sectional, edge view of afour-sheet manifolding pack utilizing record material of the presentinvention. v

The basic element of the pressure sensitive record materials of thisinvention is a sheet of record material cornprising a substantial amountof lignin uniformly distributed throughout or coated on the sheet. Thesheet is preferably paper containing residual lignin, but the lignin maybe separately added to the paper on machine, i.e., during the paperforming operation, of olf machine, i.e., at a stage subsequent to thepaper formation. The latter would include, e.g., coating, sizing orimpregnating the paper with a lignin containing material.

f 3,450,553 Patented June 17, 1969 The chemical composition of lignin isnot knownwith precision. Lignin is the major non-carbohydrateconstituent of wood and woody plants and may comprise about 25% of suchmaterials. It functions as a natural plastic binder for the cellulosicfibers of wood, straw, etc. Rather than referring to a specificcompound, the term lignin actually is a collective term for a group orsystem of compounds of high molecular weight. A summary of thefunctional groups and interunit linkages in lignin as it is now known isdescribed by E. Adler in Das Papier 15, page 604 (1961). The colorforming group is generally regarded to be the coniferyl aldehyde group.

Paper containing lignin may be readily produced by controlling thepulping action during the paper making process. During the manufactureof paper pulp from wood (there is no lignin in cotton), straw, etc., bythe conventional chemical processes, such as the sulfate (kraft), sulteand soda pulping a certain amount of the hemicelluloses and lignin areremoved. In the less eX- pensive types of paper produced by the milderchemical processes commonly referred to as semi-chemical or chemi-groundwood, a very large percentage of the lignin originally present in theoriginal fiber (wood, straw, etc.) is retained in the pulp.

As an example, suitable papers were prepared from the following pulps onthe web former of the Institute of Paper Chemistry:

(l) Hardwood unbleached sulte (Magnite Process),

(2) Softwood unbleached sulte (Mitscherlich Process),

(3) Hardwood neutral sulte semi-chemical,

(4) Hardwood chiami-groundwood, and

(5) Softwood groundwood from chips given a mild sulte-bisulftepretreatment.

In newsprint or ground wood papers, almost all of the lignin in theoriginal wood is present unchanged in the final paper. Such low costpapers containing significant amounts of lignin are especially useful inthe present invention. However, it should be understood that other papermaterials may also be used and that the lignin may be separatelyintroduced or impregnated into the paper during or after its formation.This, of course, is a much less eicient method for producing the lignincontaining paper sheet than by conducting a pulping operation whichresults in a paper containing a substantial or effective amount oflignin.

The color precursor which reacts with lignin to produce the visiblereaction products may be any of a wide variety of compounds andcompositions. The compounds of particular value include certainphenolics, aromatic bases, heterocyclics and inorganic materials.

Representative of the phenolics is phloroglucinol which rapidly forms anintense purple-red color with lignin in the presence of aqua HCl.Similarly 3-hydroxyphenyl ureau products an intense orange color.

Representative of the aromatic bases is aniline hydrochloride whichrapidly forms an intense yellow with lignin in the presence of water.Similarly 4-aminophenylglycine hydrochloride yileds an orange-red colorand N,N dimethyl p phenylene-diamine hydrochloride yields an intensepurple.

Representative of the heterocyclics is 3-aminopyridine which rapidlyforms an orange color with lignin in the presence of aqua HC1. Similarlyskatole forms a deep purple color, 3,4-dimethyl-5-pyrazolone an orangecolor, and Z-methylindole a deep purple.

Representative of the inorganics is cobalt thiocyanate which rapidlyforms a deep blue with lignin bearing papers in the presence ofmoisture. The use of this compound in combination with one or more ofthe precursors cited above provides outstanding color formation uponreaction with lignin.

Many other compounds are known which react with lignin to provide abroad range of color possibilities. In some cases, however, the rate ofcolor formation is too slow to be practically useful alone as a pressuresensitive color precursor, Many combinations of precursors are possiblewhich provide a wide range of color possibilities from bright blues,greens, and yellows, intense reds and purples through near blacks.

As noted above, the present invention lends itself to the formation ofsingle or multiple sheet pressure sensitive record systems. Referring toFIGURE 1 of the drawdrawing, there is illustrated a pressure sensitiverecord system comprising a single element 10. The element comprises asheet of paper 11 containing lignin. As described above, the lignin maybe left in paper manufactured from wood or other fibrous material, e.g.,straw, not rags or cotton, by controlling the pulping process, or may beseparately added to the cellulosic fibers. In the embodiment of FIGURE1, color precursor is distributed throughout the paper in a passive, butpressure-activatable form, preferably in the form of encapsulateddroplets 12 of the color precursor or the color precursor in a suitablesolvent. By encapsulating the color precursor in a rupturable capsule,the system is rendered passive during normal handling, until thecapsules are ruptured by pressure which releases the precursor intocontact with lignin to produce the desired reaction. The paper base mayalso contain various whitening agents or other pigments or dyes, so thata good contrast is provided between the paper and the reaction productsof the color precursor with lignin. Thus, the sheet may be tinted togive good contrast with the colored reaction products, e.g., it may betinted pastel green for a red color former.

As shown in FIGURE 2, the record element may comprise a color precursor12 coated on the surface of a sheet of paper 13 which contains lignin.The color precursor may again be encapsulated or otherwise renderedpassive under normal handling conditions, by being encapsulated orentrapped in a pressure-rupturable layer or film of binder material 15.Upon application of writing or printing pressure to a surface of element20 precursor 12 is exuded from film 15 and is adsorbed into thesubstrate where it reacts with the lignin present.

The materials of the present invention may also be utilized by producinghighly efiicient manifolding packs as illustrated in FIGURES 3 and 4.

The system illustratedin FIGURE 3 comprises an assembly of two sheets 31and 32. The top sheet 31 is provided with a surface coating 33 which isat least partially pressure transferable and contains a color precursorof the type described above. The coating may comprise a solution oremulsion of a film forming material 34, such as polyvinyl alcohol, nylonor other resinous material containing dispersed or encapsulated globulesof a liquid or fiowable precursor or a solution of a precursor 35.Separate receiving sheet 32 is a paper sheet containing lignin. Pressureon selected portions of an exposed surface of assembly 30, as by writingor typing, causes portions of coating 33 to be transferred to sheet 32where the precursor reacts with lignin in the paper bringing about thedesired color forming reaction. Entire hlm 33 need not be transferred itonly being necessary that the film be ruptured or compressed so that asufficient amount of the precursor 35 is exuded and transferred to sheet32 for reaction with the lignin in that sheet.

Since in many cases pressure is applied to the upper surface of sheet 31by means of a type bar, pen, pencil or other stylus which makes its ownmark, it may not be necessary that sheet 31 contain lignin to form itsown reaction marking. However, the top sheet could be of the type shownin FIGURE 1, impregnated with sufficient color precursor so that some ofit would be transferred under pressure to an underlying receiving sheet,such as sheet 32 in FIGURE 3, and some would react in the body of thesheet itself.

A more complicated manifolding assembly of three elements is illustratedin FIGURE 4. Top element 41 comprises a paper sheet 45 containing ligninand dispersed color precursor 46 in a passive condition. The lowersurface of the paper sheet is coated with a layer 47 which is at leastpartially pressure transferable and also contains color precursor 48.Element 42 which is in surface contact with element 41 comprises a papersheet 45 containing lignin and a surface coating 47 which is pressuretransferable and contains color precursor 48. Element 43 comprises onlya paper sheet containing lignin. If desired, films or coatingscontaining precursor may also be carried on the upper surfaces of sheets32, 33 and 34 in a passive condition. Under pressure, the precursorenters a color forming reaction with lignin, both in the carrying sheetand the adjacent sheet.

Upon the application of pressure to the upper element 41 it will be seenthat a color-forming reaction is triggered in that sheet and in each ofthe underlying sheets. The reaction in sheet 41 is brought about byactivation of the passive color precursor 46 within the paper sheet 41itself. The color-forming reaction in the other sheets takes place byvirtue of transfer of color precursor from the surface of a contactingsheet into the body of the adjacent lignin-containing paper sheet. i

It will be obvious to those skilled in the art that variousmodifications may be made in the character and arrangement of theindividual record elements and manifolding packs of the presentinvention.

EXAMPLE A paper sheet containing lignin is prepared by the conventionalchemi-ground wood process and contains about 20% residual lignin.

Micro-encapsulated cobalt thiocyanate is dispersed in a solution ofpolyvinyl alcohol, the solution is coated on the surface of the paperand dried. This forms a film of polyvinyl alcohol containing themicrocapsules of precursor on the surface of the paper. Sufficientcapsules are dispersed to amount to about 5% by weight of the paper.

Under writing pressure, the capsules rupture and the cobalt thiocyanatereacts with the residual lignin in the paper to form a dark blue color.

Micro-encapsulation of the color precursor may be achieved by a varietyof methods. One suitable procedure is disclosed in following UnitedStates patent of the same assignee, in the name of Reyes and identifiedas U.S. Patent 3,173,878, issued on Mar. 16, 1965, and entitled Processof Making Microcapsules. The micro-encapsulated color precursor may beapplied to the lignin bearing sheet by either an on machine or offmachine operation. The on machine methods of application include beateraddition, addition at the size press or addition at the calendar stacks,and constitute the preferred low-cost method of application.

The application of a dispersion of polystyrene micro capsules in anaqueous emulsion of polyvinyl acetate at the size press comprises thepreferred on machine application for impregnating the lignin bearingsheet with the color precursor in passive form. (FIG. 1). Surfaceapplication of similar suspensions of micro-capsules can be achieved byon machine application at the calendar stacks or by an off machineapplication using conventional coating techniques such as reverse roll,air knife, etc., on the formed sheet. Off machine refers to a secondaryoperation on the finished sheet. It is usually more costly than onmachine treatment because it evolves a second separate operation.

The lignin content of a sheet may be enhanced by similarly impregnatingat the size press or surface coat- -ing with an aqueous suspension ofpurified lignin (5-10 microns in size). Cooperative Report of the U.S.Forests Products Laboratory, Paper Ind. 27, No. 11:1683-89 (February1946).

Addition of passive color precursor at the paper machine to a newsprintfurnish makes possible a very low cost pressure sensitive sheet.

The optimum concentration of lignin in the paper sheet ranges from aminimum of about 5% by weight of the base sheet to 35% or higher.Distribution of both color precursor and lignin throughout the sheet ofcourse are of primary importance. Both reactants may also be surfacecoated and, if so, the concentration required will be less than if oneor both is distributed throughout the base paper.

It will be obvious to those skilled in the art that certainmodifications may be made in the composition and procedures describedabove without departing from the spirit or scope of the invention asexpressed in the following claims.

What is claimed is:

1. A pressure sensitive record material comprising a sheet of papercontaining at least about tive percent lignin, and

a color precursor substantially colorless which reacts with lignin underwriting pressure to form visible reaction products, said reactantincluding at least one compound selected from the group consisting ofphloroglucinol, 3-hydroxyphenyl urea, aniline hydrochloride,4-aminophenylglycine hydrochloride, N,N dimethyl P phenylene diaminehydrochloride, 3 aminopyridine, skatole, 3,4 dimethyl-S-pyrazolone,Z-methylindole, and cobalt thiocyanate.

2. The pressure sensitive record material of claim 1 wherein saidreactant is distributed substantially uniformly throughout the body ofsaid sheet of paper.

3. The pressure sensitive record material of claim 2 wherein saidreactant is contained in pressure rupturable capsules.

4. The pressure sensitive record material of claim 3 wherein saidcapsules are substantially uniformly distributed throughout the body ofsaid sheet of paper.

5. The pressure sensitive record material of claim 1 wherein saidreactant comprises cobalt thiocyanate.

6. The pressure sensitive record material of claim 5 wherein saidreactant further comprises an additional organic precursor.

7. The pressure sensitive record material of claim 1 wherein said ligninis present in the body of said sheet of paper and said reactant ispresent in a coating on the surface of said sheet of paper.

8. The pressure sensitive record material of claim 1 wherein both saidlignin and said reactant are present in a coating on the surface of saidsheet of paper,

9. The pressure sensitive record material of claim 1 wherein saidreactant is present in a coating on a substrate other than said sheet ofpaper and is transferable under writing pressure from to said sheet ofpaper to react with said lignin to form visible reaction products.

10. A manifolding assembly comprising a plurality of pressure sensitiverecord materials of the type defined in claim 1.

11. The pressure sensitive record material of claim 1 wherein thereactant is suiiicient to amount t0 about ve percent by weight of thepaper.

12. The pressure sensitive record material of claim 1 wherein saidreactant is phloroglucinol.

13. The pressure sensitive record material of claim 1 wherein saidreactant is 3-hydroxyphenyl urea.

14. The pressure sensitive record material of claim 1 wherein saidreactant is aniline hydrochloride.

15. The pressure sensitive record material of claim 1 wherein saidreactant is 4-aminophenylglycine hydrochloride.

16. The pressure sensitive record material of claim 1 wherein saidreactant is N,N-dimethyl-P-phenylene-diamine hydrochloride.

17. The pressure sensitive record material of claim 1 wherein saidreactant is 3-aminopyridine.

18. The pressure sensitive record material of claim 1 wherein saidreactant is skatole.

19. The pressure sensitive record material of claim 1 wherein saidreactant is 3,4-dimethyl-5-pyrazolone.

20. The pressure sensitive record material of claim 1 wherein saidreactant is 2-metl1ylindole.

21. The pressure sensitive record material of claim 1 wherein saidreactant is cobalt thiocyanate.

References Cited UNITED STATES PATENTS 2,929,736 3/1960 Miller et al.117-36.9 2,972,547 2/1961 Tien 117-36.2 3,020,171 2/1962 Bakan et al1l7-36.8 3,179,600 4/ 1965 Brockett 1l7-36.8 3,305,382 2/1967 Orinik117-363 MURRAY KATZ, Primary Examiner.

U.s. C1. X.R. 117-363, 155

